# Define here the models for your spider middleware
#
# See documentation in:
# https://docs.scrapy.org/en/latest/topics/spider-middleware.html
import random

from scrapy import signals
from scrapy.http import HtmlResponse

# useful for handling different item types with a single interface
from itemadapter import is_item, ItemAdapter


# 蜘蛛中间件
from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support import expected_conditions
from selenium.webdriver.support.wait import WebDriverWait

from myspider import settings


class MyspiderSpiderMiddleware:
    # Not all methods need to be defined. If a method is not defined,
    # scrapy acts as if the spider middleware does not modify the
    # passed objects.

    @classmethod
    def from_crawler(cls, crawler):
        # This method is used by Scrapy to create your spiders.
        s = cls()
        crawler.signals.connect(s.spider_opened, signal=signals.spider_opened)
        return s

    def process_spider_input(self, response, spider):
        # Called for each response that goes through the spider
        # middleware and into the spider.

        # Should return None or raise an exception.
        return None

    def process_spider_output(self, response, result, spider):
        # Called with the results returned from the Spider, after
        # it has processed the response.

        # Must return an iterable of Request, or item objects.
        for i in result:
            yield i

    def process_spider_exception(self, response, exception, spider):
        # Called when a spider or process_spider_input() method
        # (from other spider middleware) raises an exception.

        # Should return either None or an iterable of Request or item objects.
        pass

    def process_start_requests(self, start_requests, spider):
        # Called with the start requests of the spider, and works
        # similarly to the process_spider_output() method, except
        # that it doesn’t have a response associated.

        # Must return only requests (not items).
        for r in start_requests:
            yield r

    def spider_opened(self, spider):
        spider.logger.info('Spider opened: %s' % spider.name)


class JingdongDownloaderMiddleware:

    def __init__(self):
        # options = webdriver.ChromeOptions()
        # options.add_argument('--headless')
        # self.browser = webdriver.Chrome(options)
        self.browser = webdriver.Chrome()
        self.wait = WebDriverWait(self.browser, 10)

    @classmethod
    def from_crawler(cls, crawler):
        # This method is used by Scrapy to create your spiders.
        s = cls()
        crawler.signals.connect(s.spider_opened, signal=signals.spider_opened)
        return s

    def spider_opened(self, spider):
        spider.logger.info('Spider opened: %s' % spider.name)

    def process_request(self, request, spider):
        self.browser.get(request.url)
        self.wait.until(
            expected_conditions.presence_of_element_located(
                (By.CSS_SELECTOR, '#J_goodsList > ul > li > div.gl-i-wrap')
            )
        )
        return HtmlResponse(
            url=request.url,
            body=self.browser.page_source,
            request=request,
            encoding='utf-8',
            status=200
        )

    def process_response(self, request, response, spider):
        return response

    def process_exception(self, request, exception, spider):
        pass


# 下载中间件 ---> 代理模式 ---> 拦截过滤器（拦截请求、响应、异常，并提供额外的功能）
# 中间件里面这些方法都属于回调方法（callback method）
# 正常调用：我们写的程序调用系统为我们提供的函数（方法）
# 回调：我们写一个函数（方法），在适当的时候系统会主动调用我们写好的函数（方法）
class MovieDownloaderMiddleware:
    # Not all methods need to be defined. If a method is not defined,
    # scrapy acts as if the downloader middleware does not modify the
    # passed objects.

    @classmethod
    def from_crawler(cls, crawler):
        # This method is used by Scrapy to create your spiders.
        s = cls()
        crawler.signals.connect(s.spider_opened, signal=signals.spider_opened)
        return s

    def process_request(self, request, spider):
        # Called for each request that goes through the downloader
        # middleware.

        # Must either:
        # - return None: continue processing this request
        # - or return a Response object
        # - or return a Request object
        # - or raise IgnoreRequest: process_exception() methods of
        #   installed downloader middleware will be called
        # request.meta['proxy'] = 'socks5://127.0.0.1:1086'
        # request.meta['proxy'] = random.choice(settings.PROXIES)
        # request.headers['Cookie'] = '...'
        return None

    def process_response(self, request, response, spider):
        # Called with the response returned from the downloader.

        # Must either;
        # - return a Response object
        # - return a Request object
        # - or raise IgnoreRequest
        return response

    def process_exception(self, request, exception, spider):
        # Called when a download handler or a process_request()
        # (from other downloader middleware) raises an exception.

        # Must either:
        # - return None: continue processing this exception
        # - return a Response object: stops process_exception() chain
        # - return a Request object: stops process_exception() chain
        pass

    def spider_opened(self, spider):
        spider.logger.info('Spider opened: %s' % spider.name)
